Shuffle Button for Podcasts

### What problem does this address?

For instance, let's say I have played all episodes of a podcast but now I want to listen to a random episodes. For that purpose, I'm proposing a shuffle feature.

### What is your proposed solution?

Adding a shuffle button to play random episodes from any podcast or archive.

### Did you search for existing feature suggestions?

- [X] I have searched for existing feature suggestions.

The issue names no files, tests, or entry points. Start by locating the podcast and archive playback flows and their existing playback controls, then define the shuffle behavior for both contexts and verify that a shuffle button can select random episodes as proposed.

Written by the indexing model from the issue text.